1. Field of the Invention
The invention relates to a device for variable activation of valves for internal combustion engines.
2. The Art
Devices for variable activation of valves are known in the art as shown, for example, in the document DE 100 61 618 A1. This device is arranged in a cylinder head having a camshaft mounted in a fixed location, having valves that close by means of spring force. Each of the valves has a stroke transfer arrangement associated with it. The valves are guided in a fixed location in the cylinder head. An element that is adjustable with regard to the valve stroke setting is arranged in the cylinder head, in a fixed location, and a control cam, in each instance, in an axial plane, one running after the other.
An intermediate member is prismatically supported on the element that can change positon, both on its support cam and on its control cam, with a non-positive lock. This member is guided to pivot during the stroke movement and, in this regard, to slide on the two cams.
Furthermore, the intermediate member is engaged with one of the cam levers of the camshaft, as well as with a stroke transfer arrangement for a valve. The control cam determines the movement path of the intermediate member during the stroke of the cam lever, as a function of the pivot position of the adjustable element. The control cam thereby determines the size of the stroke created by the stroke transfer arrangement at the valve.
The design configuration of this embodiment is limited, because the support cam and the control cam are arranged to run consecutively on the element that can change its position, and thereby there must be a fixed distance between the two prismatic engagement lines at the support cam and the control cam as well as at the intermediate member.
The invention relates to a device for variable activation of one or two valves activated in parallel, wherein the valves have a compact construction, and wherein interacting parts are preferably in roller engagement.
This design is achieved by creating a structure which includes a support cam or support cams arranged parallel to one another, wherein these support cams are set back radially relative to a control cam. In this case, these cams are in engagement with one slide support of an intermediate member, or one each, such that the prismatic engagement lines on the support cam and the control cam as well as the intermediate member can have a smaller distance between them. This allows an advantageous configuration of the intermediate member. At the same time, there can be an axial guidance of the intermediate member on the element that can change its position. In this case, the support cams are arranged to be axially offset relative to the control cam.
In an embodiment of the invention, a set of slide supports of an intermediate member are arranged on both sides of a control cam and of a circumference region that follows it. These supports engage with the radially set-back support cams and also engage axially with the subsequent circumference region of the control cam. Thus, there is a stable three-point support for the intermediate member on the element that can change position.
In the case of a device for a parallel activation of two valves, the control cam of the changeable element can be arranged axially between two stroke transfer arrangements for the two valves. In this case, a pressure bridge is in engagement with one of the stroke transfer arrangements, in each instance, on the intermediate member, axially next to the slide supports of the intermediate member. This type of an arrangement is particularly compact and does not require any particular construction height.
There can be a roller engagement of the slide supports arranged on the intermediate member. In this embodiment, the support cam or cams are configured as a roller mounted to rotate or pivot about a pivot axis of the changeable element.